A rice BR-deficient mutant, Ebisu dwarf (d2), is caused by loss-of-function of a new member of cytochrome P450.

Abstract

We isolated a new BR-deficient mutant, Ebisu dwarf (d2), in rice. d2 showed dwarfism with specific inhibition of the 2nd internode. Detailed feeding experiment revealed 6-Deoxo3DT, 3DT and their downstream intermediates effectively bended the lamina joint of d2. The endogenous level of BRs in d2 supported the result of feeding experiment. These indicate that d2 may be deficient in the conversion from 6-DeoxoTE to 6-Deoxo3DT and from TE to 3DT. D2 was localized at the short arm of rice chromosome 1 and predicted to encode a cytochrome P450. D2 is highly homologous to ROT3, whose function is still unclear. D2 is negatively regulated by BL and is highly expressed in leaf blade and elongation stem. These results suggest that D2 is a new member of P450s, which may catalyze the oxidation of C3-hydroxyl in the late step of BR biosynthesis.
This work was in part supported by PROBRAIN.